NEST from conda without MPI support

[jhnnsnk]

NEST 3.4 from conda is not compiled with MPI as it was the case earlier. Local network simulations break.
See: https://nest-simulator.readthedocs.io/en/stable/installation/conda_forge.html#conda-forge-install

[espenhgn]

This issue can be moved to https://github.com/conda-forge/nest-simulator-feedstock issues, and/or be discussed with @steffengraber who maintains that feedstock.
On my end, I've always compiled and used NEST with MPI, also on my local machine, and I cannot imagine being the only user doing that. Having a conda-forge package for NEST+MPI would be quite convenient.